Welcome! Please see the About page for a little more info on how this works.
In various places Clojure accepts classnames as {{String}}, eg. in {{gen-class}} or type hints. However it does not in {{extend-protocol}}. This does not allow simple specification of array types.
See also here: (link: http://groups.google.com/group/clojure/browse_thread/thread/722a0c09d02bb0ac)